Update neutron to 9.0.0~b2

Update neutron to 9.0.0~b2

Xenial:
- Update requirements based on project requirements
- Source [0]
- Add missing dependencies (radvd, python-openvswitch, python-pyroute2)
  Commits a5a14ee 918a100 f28290b
- Add doc package and git as a build dependency

Centos7:
- Update requirements based on project requirements
- Add doc package
- Remove neutron-bgp-dragent service from spec and sources

[0] http://anonscm.debian.org/git/openstack/neutron.git/?h=debian%2Fnewton

Change-Id: Ib914b36b82e2e1e3628bd2cfeac3ac8b5a46e8db